Abstract:

Introduction:

• The purpose of this essay is to use topographic map interpretation methods to explore western South Dakota Battle Creek-French Creek drainage divide area landform origins. Map interpretation methods can be used to unravel many geomorphic events leading up to formation of present-day drainage routes and development of other landform features. While each detailed topographic map feature provides detailed evidence to be explained, the solution must be consistent with explanations for adjacent area map evidence as well as solutions to big picture map evidence puzzles. I invite readers to improve upon my solutions or to propose alternate solutions that better explain evidence and are also consistent with adjacent map area and big picture evidence. Readers may do so either by making comments here or by writing and publishing their own essays and then by leaving a link to those essays in a comment here.

• This essay is also exploring a paradigm in which erosional landforms are interpreted as evidence left by immense glacial melt water floods. Implied in that interpretation is the immense floods were derived from a thick North American ice sheet that created a deep “hole” in the North American continent and also melted fast. The previously unexplored paradigm being tested in this and similar essays is a thick North American ice sheet, comparable in thickness to the present day Antarctic ice sheet, occupied approximately the North American region usually recognized to have been glaciated and through its weight and erosive actions created a “deep” North American “hole”, through its weight and deep erosion (and perhaps deposition) along major south-oriented melt water flow routes caused significant crustal warping and tectonic change, through its action of melting fast produced immense floods that flowed across the continent, and through its action of melting fast systematically opened up space in the ice sheet created “hole” so headward erosion of newly developed north-oriented drainage systems captured immense south-oriented melt water floods and diverted immense melt water floods north into space the ice sheet had once occupied.

• If this previously unexplored paradigm is correct the geographic region explored by this essay should contain evidence of immense floods that were captured by headward erosion of new valley systems so as to cause the floods to flow in a different direction. Ability of this previously unexplored paradigm to explain Battle Creek-French Creek drainage divide area landform evidence will be regarded as evidence supporting the “thick ice sheet that melted fast” paradigm.

Battle Creek-French Creek drainage divide area general location map

Figure 1: Battle Creek-French Creek drainage divide area general location map (select and click on maps to enlarge). National Geographic Society map digitally presented using National Geographic Society TOPO software.

Figure 1 provides a general location map for the Battle Creek-French Creek drainage divide area. The map illustrates an area in western South Dakota. Immediately west of the figure 1 map area is the state of Wyoming. Battle Creek and French Creek both originate in the Black Hills southwest of Rapid City, South Dakota and flow southeast to join the northeast-oriented Cheyenne River, just west of the Badlands National Park. Rapid Creek is not labeled, but it is the unlabeled southeast-oriented stream immediately south of Boxelder Creek and flows through Rochford, Silver City, Rapid City, and Farmingdale, South Dakota. Spring Creek is the unlabeled stream immediately south of Rapid Creek and flows through Hill City and near the Stratobowl. Battle Creek is the unlabeled stream immediately south of Spring Creek and flows through Keystone and Hermosa. French Creek is the unlabeled stream immediately south of Battle Creek and flows through Fairburn, South Dakota. Battle Creek and French Creek are two of several streams shown on figure 1 flowing southeast from the Black Hills to join the northeast-oriented Cheyenne River east of the Black Hills. North of Boxelder Creek is Elk Creek, which is labeled in figure 1.

• The Spring Creek-Battle Creek drainage divide area, Rapid Creek-Spring Creek drainage divide area, Boxelder Creek-Rapid Creek drainage divide area, Elk Creek-Boxelder Creek drainage divide area, Belle Fourche River-Elk Creek drainage divide area north of Elk Creek, Whitewood Creek-Bear Butte Creek and Spearfish Creek-Whitewood Creek essays describe drainage divide areas west and north of the Battle Creek-French Creek drainage divide area and can be found under Black Hills region on the sidebar category list. This essay interprets Battle Creek-French Creek drainage divide area landform origins in the context of an immense southeast oriented flood that flowed across the entire figure 1 map area and that was systematically captured by headward erosion of deep northeast-oriented valleys, which diverted flood waters further and further northeast and north. The source of the southeast-oriented flood water cannot be determined from evidence presented here. However, based on numerous other Missouri River drainage basin landform origins research project essays published on this website the flood occurred before and/or while the Black Hills area was being uplifted and the floods can be traced headward to a North American ice sheet location. Rapid melting of a thick North American ice sheet located in a deep “hole” would explain the flood water source and also why deep valleys eroded west and southwest to capture southeast-oriented flood waters to divert flood waters further and further northeast and north into space in the deep “hole” the rapidly melting ice sheet had once occupied. In addition, presence of a thick North American ice sheet in a deep “hole” north and east of the Black Hills might explain crustal warping that uplifted the Black Hills dome during or even after an immense southeast-oriented flood. Uplift of the Black Hills dome may have been accelerated by crustal unloading as flood waters deeply eroded the Black Hills region and removed overlying rock layers.

Battle Creek-French Creek drainage divide area detailed location map

Figure 2: Battle Creek-French Creek drainage divide area detailed location map. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 2 provides a slightly more detailed location map for the Battle Creek-French Creek drainage divide area. Custer County and Pennington County are located in western South Dakota. Green areas represent Black Hills National Forest lands, which are generally located in the Black Hills upland region. Battle Creek originates in the Black Hills upland area in southern Pennington County, northwest of Mount Rushmore National Park and flows through Keystone, South Dakota in southern Pennington County. Grace Coolidge Creek is a Battle Creek tributary flowing from the northern Custer State Park area. French Creek originates northwest of Custer, South Dakota and flows through Custer State Park to Fairburn and then to the Cheyenne River. West of the Battle Creek origin French Creek headwaters share a drainage divide with northeast oriented Spring Creek headwaters and four detailed maps below illustrate that drainage divide. Figure 2 does not provide enough detail to make observations about Battle Creek-French Creek drainage divide landform origins in the Black Hills area and such observations need to be made from more detailed maps below. However, east of the Black Hills figure 2 shows southeast oriented Rapid Creek tributaries flowing from the north. Further, figure 2 shows several southeast oriented tributaries to the northeast oriented Cheyenne River. Also figure 2 shows northwest-oriented tributaries to the northeast oriented Cheyenne River. Detailed maps below further illustrate this northwest-southeast tributary orientation. This predominance of southeast and northwest oriented tributaries to major streams on the plains east of the Black Hills is evidence major east, northeast, and north-oriented stream valleys eroded headward across multiple southeast-oriented flood flow routes, such as might be found in a large-scale anastomosing channel complex. Headward erosion of deep northeast and east oriented valleys (or of even a southeast-oriented valley) across such a complex of southeast-oriented flood flow channels would have captured the southeast-oriented flood waters and enabled southeast-oriented tributary valleys to erode headward from the newly eroded and deep stream valley walls along the captured southeast-oriented flood flow channels. At the same time capture of the southeast-oriented flood flow would have beheaded southeast-oriented flood flow routes and flood waters on the northwest ends of those beheaded flood flow channels would have reversed flow direction to flow northwest into the newly eroded and deeper stream valleys. Because the channels were anastomosing (meaning they were interconnected) reversed flow on beheaded flood flow routes often captured flood waters from yet to be beheaded flood flow routes further to the south or southwest. Capture of water from such yet to be beheaded flood flow routes frequently provided sufficient water to erode significant northwest-oriented tributary valleys.

Spring Creek-French Creek drainage divide area northwest of Custer, South Dakota

Figure 3: Spring Creek-French Creek drainage divide area northwest of Custer, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 3 illustrates the Spring Creek-French Creek drainage divide area north and west of Custer, South Dakota. Spring Creek flows southeast from the figure 3 north center edge to join Vanderlehr Creek and then flow east before turning northeast at Oreville. French Creek is the stream flowing through Custer to Stockade Lake at the figure 3 east edge (south). The South Fork French Creek originates between Round Mountain and Mile High Hill and flows southeast to the south-oriented North Fork French Creek. Sourdough Draw west of Round Mountain drains south-southwest to Hell Canyon and eventually to the Cheyenne River south of the Black Hills (French Creek and Spring Creek both flow to the Cheyenne River east of the Black Hills).  The North Fork French Creek originates south of Bear Mountain and flows southeast and south to join the Middle Fork and the South Fork. Ruby Creek flows south-southeast from the Vestal Springs area to join French Creek west of Custer. Note how the East Fork Ruby Creek valley is linked near Berne by a through valley used by the highway and railroad to north-oriented Tenderfoot Gulch, which drains to Spring Creek. That through valley is evidence water once flowed south from what is today the Spring Creek drainage basin to what is now the French Creek drainage basin. Similar through valleys linking south-oriented French Creek tributary valleys with Spring Creek tributary valleys can be seen in the Vestal Springs area and south of Bear Mountain. Several through valleys cross the Sourdough Draw-French Creek drainage divide and provide evidence water once flowed east from what is today the Hell Canyon drainage basin to what is today the French Creek drainage basin. Detailed maps below illustrate through valleys near Vestal Springs, near Berne, near Sylvan Lake in the figure 3 northeast corner, and north of Stockade Lake in the figure 3 southeast corner. These through valleys are relics from an earlier drainage system that once crossed the figure 3 map area. The multiple through valleys provide evidence the earlier drainage system was an anastomosing complex of channels, such as would be produced by an immense flood flowing across the figure 3 map region. Detailed maps below illustrate how headward erosion of deep east-oriented valleys captured the flood flow and diverted the flood water east. Figure 3 evidence illustrates that the deep south-oriented Hell Canyon-Sourdough Draw valley also eroded north to capture east-oriented flood waters and to divert the water south.

Spring Creek-French Creek drainage divide area near Vestal Springs

Figure 4: Spring Creek-French Creek drainage divide area near Vestal Springs. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 4 illustrates the Spring Creek-French Creek drainage divide area near Vestal Springs. The North Fork French Creek flows southeast from the figure 4 west edge (north half) and the Middle Fork French Creek flows southeast from the figure 4 west edge (south half). South of Vestal Springs are headwaters of south oriented Ruby Creek. The south oriented valley in the figure 4 southeast corner drains to Ruby Creek. North of Vestal Springs is east and north oriented Loues Creek, which flows north to join Vanderlehr Creek and then join Spring Creek (see figure 3). East of Vestal Springs are northeast and east-oriented headwaters of Graveyard Gulch, which will be seen again in figure 5 below. Note how all valleys are interconnected by what appear to be shallow through valley or gaps or passes crossing all drainage divides. For example in the figure 4 southeast corner two such passes or through valleys link a northwest-oriented Graveyard Gulch tributary with the south oriented valley draining to Ruby Creek. Or, note the through valley connecting Loues Creek headwaters near the Roetzel Deer Camp with the North Fork French Creek valley. Or, note the shallow through valley just west of Vestal Springs (where the 1611 foot elevation number is located) connecting Ruby Creek headwaters with headwaters of a northeast and north oriented Loues Creek tributary. These through valleys were all eroded by water and can be best be explained in the context of a south- and southeast-oriented anastomosing channel complex that was systematically dismembered by headward erosion of deeper north and northeast oriented valleys. By systematically dismembered I mean the French Creek tributary valleys eroded headward into the region first, the Tenderfoot Gulch-Graveyard Gulch valley eroded headward into the region second, the Loues Creek valley eroded headward into the region next, and the Vanderlehr Creek valley eroded headward into the region next. As each valley eroded headward into the region flood flow patterns were changed, with north-oriented valleys being eroded by reversed flow on beheaded flood flow routes, especially those reversed flow routes able to capture flood waters from yet to be beheaded south-oriented flood flow routes.

Spring Creek-French Creek drainage divide area near Berne

Figure 5: Spring Creek-French Creek drainage divide area near Berne. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 5 illustrates the Spring Creek-French Creek drainage divide or the Tenderfoot Gulch-East Fork Ruby Creek drainage divide area near Berne. The north and northeast-oriented Tenderfoot Gulch valleys drain to Spring Creek north of figure 5. South-oriented drainage at Berne flows to the East Fork Ruby Creek, which flows to south-oriented Ruby Creek and then to French Creek. South-oriented Laughing Water Creek originates near the Crazy Horse carvings, which are located at Thunderhead Mountain north of Berne, and flows south and southeast to join French Creek at Custer, which is located south of figure 5. An unnamed stream (Willow Creek) flows from a large southeast-oriented escarpment-surrounded basin to the figure 5 southeast corner. The large escarpment-surrounded basin is an abandoned headcut, which was eroded by southeast-oriented flood flow. The highway and railroad are located in a prominent north-south through valley linking the Spring Creek drainage basin with the French Creek drainage basin. That prominent north-south through valley (along with the Laughing Water Creek valley) probably eroded north to capture southeast-oriented flood flow that had been eroding the large Willow Creek valley headcut. Other higher level through valleys (or saddles in ridges) link the north- and south-oriented drainage networks. For example just north of the Old Mike Mine (east of Berne) a high-level through valley links the Laughing Water Creek valley with the Willow Creek valley head, which probably was one of the southeast-oriented flood flow routes beheaded by headward erosion of the deep Laughing Water Creek valley. Or northwest of Berne a high-level through valley links the East Fork Ruby Creek with a northwest-oriented Graveyard Gulch tributary valley. That valley was probably initiated by southeast-oriented flood flow and then flow was reversed when the deep northeast-oriented Tenderfoot Gulch-Graveyard Gulch valley eroded southwest from the deep Spring Creek valley. Reversed flood flow, which captured yet to be beheaded southeast-oriented flood flow on the alignment of the south-southeast oriented valley to the southwest then eroded the northwest-oriented Graveyard Gulch tributary valley. Erosion of this figure 5 map region required immense quantities of water flowing in ever-changing and interconnected anastomosing channels, and also requires that Black Hills uplift above the surrounding plains region had not yet occurred. Other explanations do not explain the evidence.

Spring Creek-French Creek drainage divide area near Sylvan Lake

Figure 6: Spring Creek-French Creek drainage divide area near Sylvan Lake. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 6 illustrates the Spring Creek-French Creek drainage divide area near Sylvan Lake, located near the Needles, which is one of the Black Hills highest locations. The southeast-oriented Willow Creek valley seen in figure 5 is located in the figure 6 southwest corner and drains to French Creek. A deep southwest-oriented valley drains from just south of the Sylvan Lake area to the Willow Creek valley, although Sylvan Lake drains northwest to Spring Creek (named Sunday Gulch north of figure 6 and linked by a well-defined through valley to the Palmer Creek valley, which is a northeast-oriented Spring Creek tributary valley also located north of figure 6). Other drainage south of the Needles is to French Creek. Iron Creek, which drains from the Cathedral Spires area to the figure 6 east edge (center), is a Battle Creek tributary. Several through valleys link the northwest-oriented stream valley draining Sylvan Lake with the southwest-oriented Willow Creek tributary valley. While not spectacular compared to other valleys on figure 6 these through valleys provide evidence water once flowed in multiple channels across what is now the Spring Creek-French Creek drainage divide just south of Sylvan Lake. Several southeast-oriented valleys drain to a southwest-oriented stream draining to the figure 6 south center edge (that southwest-oriented valley is illustrated again in figure 7 below). Headwaters of these southeast-oriented streams are also linked by through valleys to the northwest-oriented Sunday Gulch valley system. The multiple through valleys crossing the present day drainage divide provide evidence large volumes water once flowed in multiple channels across what is now a high-level drainage divide. In brief south and southeast-oriented flood flow was captured by headward erosion of the deep Iron Creek valley (which probably eroded headward from the deep Battle Creek valley). Flood waters were then captured by headward erosion of the deep French Creek-Willow Creek valley, with multiple southwest-oriented Willow Creek valleys eroding headward in sequence to capture southeast-oriented flood flow. Southeast-oriented flood flow was then beheaded by headward erosion of the northeast-oriented Spring Creek-Palmer Creek-Sunday Gulch valley to reverse flood flow on what is today the northwest-oriented Sunday Gulch valley route. Reversed flow played an important role in eroding northwest-oriented valleys, which required capture of yet to be beheaded south-oriented flood flow. There were reverse flow details I have not worked out to my satisfaction and perhaps a reader can suggest an explanation or alternate explanation better explains the evidence.

Battle Creek-French Creek drainage divide area north of Stockade Lake

Figure 7 illustrates the Battle Creek-French Creek drainage divide area north of Stockade Lake, which is located southeast of the figure 6 map area and which overlaps the figure 6 map area. Southeast-oriented Willow Creek is the stream in the figure 7 southwest corner and flows to French Creek. The southwest-oriented valley originating near the figure 7 north center edge and draining to Willow Creek was seen in figure 6. It is the valley with the several southeast oriented tributaries that originated at through valleys at the drainage divide in the Needles area. The two south-oriented streams flowing to the figure 7 south center edge join French Creek. Northeast-oriented Grace Coolidge Creek flowing to the figure 7 east center edge turns southeast after leaving the figure 7 map area and eventually joins Battle Creek. Iron Creek in the figure 7 northeast corner also flows eventually to Battle Creek. Note the drainage divide between the southwest-oriented Willow Creek tributary and the two south-oriented French Creek tributaries (flowing to the figure 7 south center edge). Note how the headwaters of the south-oriented French Creek tributaries are linked by through valleys to the southwest-oriented Willow Creek tributary valley. Also note how headwaters of the two French Creek tributaries line up with alignments of southeast-oriented tributaries flowing from the Needles area to the southwest-oriented Willow Creek tributary. This evidence indicates headward erosion of the deep French Creek valley captured large volumes of southeast-oriented flood flow moving from the Needles area through the figure 7 map area. The southeast-oriented flood flow began to erode southeast-oriented valleys headward into the Needles area. Headward erosion of the deep Willow Creek valley then enabled the southwest-oriented Willow Creek tributary valley to erode northeast to capture the southeast-oriented flood flow from the Needles area and to behead flood flow that had been eroding the two French Creek valleys. What has been missed so far is the presence of the Grace Coolidge Creek headwaters along the figure 7 east (south and center) edge. Through valleys link the northeast-oriented Grace Coolidge Creek headwaters with headwaters of southwest-oriented tributaries to the easternmost of the two south-oriented French Creek tributaries. In other words, the northeast-oriented Grace Coolidge Creek valley eroded into the figure 7 map region to capture the southeast-oriented flood flow from the Needles area and then headward erosion of the deeper French Creek valley and its south-oriented tributary valley captured the flood flow, beheading flood flow to the newly eroded Grace Coolidge Creek valley.

Battle Creek-French Creek drainage divide area near Custer State Park campground

Figure 8 illustrates the Battle Creek-French Creek drainage divide area near the Custer State Park campground. Grace Coolidge Creek flows through the Custer State Park campground area and then northeast to the figure 8 northeast corner. Grace Coolidge Creek continues to flow northeast to join southeast-oriented Battle Creek. Originating in the large through valley located just south of the Custer State Park campground is (east) Dry Creek, which generally flows southeast and east to eventually reach southeast-oriented French Creek. The through valley linking the Grace Coolidge Creek valley and the (east) Dry Creek valley is related to the underlying geology, however it also provides evidence that at one time water flowing east in the Grace Coolidge Creek valley split, with some water continuing along what is today the Grace Coolidge Creek route northeast to the Battle Creek valley and some water flowing southeast along what is today the (east) Dry Creek valley route to the French Creek valley. This evidence strongly suggests the existence of anastomosing channels. Other through valleys in the figure 8 map area suggest at one time there were even more anastomosing channels. For example, in the figure 8 southeast corner there is an east oriented Dry Creek tributary with headwaters linked by a through valley with the southeast-oriented (east) Dry Creek valley. At one time water flowing southeast in the (east) Dry Creek valley split, with some water flowing along what is today the (east) Dry Creek valley route and some water flowing along what is today the east oriented Dry Creek tributary route. Also note northeast-oriented Galena Creek flowing from the figure 8 west (center south) edge to join Grace Coolidge reek northwest of the Custer State Park campground and an east and southeast-oriented (west) Dry Creek in the figure 8 southwest quadrant flowing to (east) Dry Creek in the southeast quadrant. Note how headwaters of the east and southeast-oriented (west) Dry Creek are linked by a through valley with the northeast-oriented Galena Creek valley. This evidence indicates at one time water flowing in the Galena Creek valley split, with some water flowing northeast to the Grace Coolidge Creek valley and the Battle Creek valley and some water flowing east and southeast to (west) Dry Creek valley and French Creek valley.

Battle Creek-French Creek drainage divide area near Fairburn, South Dakota

Figure 9: Battle Creek-French Creek drainage divide area near Fairburn, South Dakota. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Figure 9 illustrates the Battle Creek-French Creek drainage divide area near Fairburn, South Dakota. French Creek is the stream flowing through Fairburn and then southeast, northeast and east along the figure 9 south edge. East of figure 9 French Creek turns southeast to flow to the Cheyenne River (see figure 10). Battle Creek is the southeast-oriented stream flowing across the figure 9 northeast corner. Dry Creek (seen in figure 8) is the east-oriented stream north of Fairburn that turns southeast to join French Creek. Note how French Creek has multiple southeast-oriented tributaries. Through valleys link the southeast-oriented French Creek tributary valleys with the Battle Creek valley or with Battle Creek tributary valleys, although figure 9 details are not adequate to show such. Figure 9a below illustrates one such through valley used by the railroad north of Fairburn. The through valley links the east-oriented L 7 Draw valley, which drains to Battle Creek with a south oriented tributary draining to southeast-oriented Dry Creek and French Creek. The through valley provides evidence that at one time water flowed south in the through valley to the Dry Creek valley and the French Creek valley and also flowed east in the L 7 Draw valley to the Battle Creek valley. This through valley and others like it provide more evidence of anastomosing flood flow channels linking what are today the separate Battle Creek and French Creek drainage basins and further evidence suggesting the present day Battle Creek and French Creek valleys eroded headward to capture south and southeast-oriented flood flow and to divert the water east and southeast to some newly eroded and deeper valley east of the figure 9 map area.

Figure 9a Through valley linking L 7 Draw valley with south-oriented Dry Creek tributary valley. United States Geological Survey map digitally presented using National Geographic Society TOPO software.

Battle Creek-French Creek drainage divide area near Cheyenne River

Figure 10 illustrates the Battle Creek-French Creek drainage divide area immediately west of the Cheyenne River. The Cheyenne River is the large northeast, southeast and northeast-oriented valley flowing from the figure 10 south (east half) edge to the figure 10 northeast corner. Battle Creek is the southeast-oriented valley flowing from the figure 10 northwest quadrant to the Cheyenne River. French Creek flows through the figure 10 southwest quadrant from the figure 10 west edge to the Cheyenne River. The Cheyenne River-White River drainage divide essay describes the area east of the Cheyenne River valley and can be found under White River on the sidebar category list. Flats and tables adjacent to the Cheyenne River valley are erosion surfaces developed prior to headward erosion of the present day northeast-oriented Cheyenne River valley. Prior to Cheyenne River valley headward erosion large volumes of flood water moved southeast in the large Battle Creek and French Creek valleys to what was then the actively eroding deep White River valley (southeast of figure 10-see essays under White River on the sidebar category list for more details). Southeast-oriented flood waters flowed across the entire the figure 10 map area and eroded the erosion surfaces now preserved in the form of flats and tables standing above the deeper Cheyenne River valley. Headward erosion of the deep northeast-oriented Cheyenne River valley then captured the southeast-oriented flood flow and diverted the flood waters northeast. Headward erosion of the deep Cheyenne River valley also lowered base level causing flood waters in the Battle Creek and French Creek valleys (and in what are today other Cheyenne River tributary valleys) to erode deeper inner valleys within their broad earlier valleys. Headward erosion of the deep Cheyenne River valley captured southeast-oriented flood flow moving to the White River valley, and flood waters on the northwest ends of those beheaded flood flow routes reversed flow direction to erode what are today northwest-oriented Cheyenne River tributary valleys. Erosion of those northwest-oriented valleys was aided by flood flow from not yet captured (by headward erosion of the deep Cheyenne River valley) southeast-oriented flood flow further to the south and southwest, which was captured and then flowed northeast along what is today the northeast-oriented White River valley, and some of which spilled to the northwest into the newly eroded northeast-oriented Cheyenne River valley.

Additional information and sources of maps studied

This essay has provided only a sample of the detailed topographic map evidence supporting the flood erosion interpretation. Many additional illustrations could be provided. Readers are encouraged to look at mosaics of detailed topographic maps to see the abundance of available data. Maps used in this study were created and published by the United States Geologic Survey and can be obtained directly from the United States Geological Survey and/or from dealers offering United States Geological Survey maps. Hard copy maps can also be observed at United States Geological Survey map depositories which are located throughout the United States and elsewhere. Illustrations used here were created using National Geographic Society TOPO software and digital map data. TOPO software and map data can be obtained from the National Geographic Society and/or dealers offering National Geographic Society digital map data.